1. Field of the Invention
This invention relates in general to a method of reclaiming electric motor laminations, particularly for submersible pump motors having windings encased in epoxy.
2. Description of the Prior Art
Submersible pump electric motors are AC motors having diameters of only a few inches, but lengths up to and exceeding 30 feet. The components of such a motor include a stator stationarily mounted inside a housing. The stator contains windings through which voltage is imposed. A rotor is mounted within the stator for rotating a shaft in response to the current passing through the stator.
The stator is composed of a large number of thin, flat disks called laminations. These laminations are of a metallic material and have slots through them for wires or windings to pass. When a voltage is imposed onto the stator, the winding is excited and tends to vibrate at the frequency of imposed power source. If some means is not used to prevent movement of the wire, the resulting vibration will cause wear in the wire insulation and a wire to wire or wire to ground fault will occur.
It is customary that the stator windings be encapsulated within a material that will hold them firmly to prevent vibration. The encapsulating material must be able to withstand whatever environment in which the motor is placed. Also, the encapsulating material must have a good dialectric properties. Various materials which have been used include varnishes and epoxies.
Varnishes accomplish the desired purpose of firmly holding the windings, but due to the low viscosity of varnish, and the evaporation of solvents during the curing cycle, many voids or open spaces are left in the slots of the stator. Expoxies are more viscous and have less solvents that must escape during a curing process, so the slot voids are essentially filled with cured epoxy.
When a winding fault occurs, the laminations of the stator are usually not damaged. It is, therefore, desirable that the damaged windings be removed and the laminations reused. If the encapsulating material is varnish, there are many solvents that are useful in dissolving varnish, allowing the windings to be easily withdrawn. Many void places exist in the slots, which permit entrance of the solvent or solvent vapors. However, if the encapsulating material is epoxy, the slots are virtually full and only a small area of the epoxy is exposed to a solvent. The amount of exposed epoxy is too small to prevent destruction of the epoxy sufficient to allow withdrawal of the windings. Epoxy also forms a mechanical bond to the windings and the laminations, and the windings are not sufficiently strong to allow pulling on the windings and removal of the windings from the stator. Consequently, the laminations in epoxy filled stators are not reclaimed.